BCD-085-3 is a next step in clinical investigation of BCD-085. BCD-085 is a monoclonal antibody to interleukin 17. During BCD-085-2 trial patients with active ankylosing spondylitis will receive 40, 80 or 120 mg of BCD-085 subcutaneously at weeks 0, 1, 2, 4, 6, 8, 10, 12. Efficacy and safety parameters will be evaluated.